This invention relates to waveguiding optical fibers of the type having a core in which the index of refraction varies radially.
Such waveguiding optical fibers of the so-called graded-index type are especially useful for multimode optical transmission and will probably be used in first-generation optical communication links with light-emitting diode sources or multimode semiconductive injection lasers or multimode optically pumped dielectric host rare earth ion lasers.
Typically, in the past, the radial grading of index in such fibers has been achieved by varying the concentration of one glassy dopant in the majority glassy matrix, which is usually silica, but which may also include one or more other glassy dopants as a constant-concentration background that is useful in setting the overall guiding strength of the fiber or in determining the mechanical properties of the fiber.